They are in a large tank together along with a veiltail "Goldie", and all 3 have lived happily together for over a year without any problems. This morning though "Bronzie" wont leave "Blackie" alone, was chasing him all around the tank and every now and then Goldie would join in too. They were even jamming him in the corner of the tank just hammering him. Poor Blackie had got to the point where he was so exhausted he was just floating and I thought he was dead. His tail and fins are pretty tattered now and I have currently put him in plastic bag floating in the tank - and Bronzie is still trying to attack him through that.

I have the same problem at the moment with my fish! I took the problem fish (Daryl) out of my main tank and pit him in another and the other two are getting on fine now even though my comet was bullying the other fish aswel! I have found out that Daryl is a bad influence! If anybody can give any better long term advice I would appreciate it also!

How long have you had each fish? How long has you tank been set up? How big is this tank?

These questions could be vital to determining why this could've happened. But in general, comet and commons move much quicklier than fancies (black moor, fantail, oranda, veiltail, ryukin), so comets could potentially beat the fancies to food and bully them.

Might be a silly question but could the fish be showing off in front of each other? I mean flash is wonderful and friendly without Daryl but when I put Daryl back in the tank he turns nasty, but they are never nasty to each other! Could that be why goldiegirl only occasionally joins in?

At this stage I have completely removed blackie from the tank for a break as he isnt looking too flash.

The comet and veiltail came with the tank when I got it in December 2010. Not long after I added 8 cockabullies, 1 calico goldfish and 1 blackmoore but all the new fish except the blackmoore died within about 3-4 weeks and I still don't know why. I did everything by the books introducing them and brought a water tester kit from the aquarium specialist store, but everything was normal, and they were at a loss as to what happened too.

The tank is a fairly large 200 Litre tank. It has an undergravel filter + air pump and an aqua one filter. It has a large barrel ornament for them to hide in + some plastic plants.

My camera is out of batteries at the moment but I have added an older photo were you can see the tank in the background. It now has a couple of plastic plants added since this was taken.

your previous fish died....did you add them all at once ? this would start a mini-cycle

Goldfish may well be social but fewer than 5 can cause bullying as they do not have enough to shoal, even 2 gentle fish can get aggressive when they are of breeding age..Mixing types only exacerbates this problem

Moors are almost blind and cannot compete for food against other goldfish, this will result in an underfed fish......the other fish will sense this weakness and will become predator

Even fancies can become aggressive....Ryukins are well-known for plucking out Moors' eyes

200 litres really isn't that large....what is your filtration rate?...It should be about 2000 L/h

How do you manage the Nitrate levels? 50% weekly water change? Nitrate/Ammonia Buffer?

Live plants can help with Nitrates and give the fish somewhere to hide

For now I should quarantine the moor, and consider another tank for the comet. If you decide to keep the moor and the fancy together you might have to hand feed the moor to ensure that he gets enough food

"...They are best kept in species tanks, not mixed with other species of fish or invertebrates, and are best either kept singly or in groups over 4-5. In pairs or trios they are likely to bully and fin nip one another, especially when spawning season comes around. It is also strongly recommended to not mix long-bodied Common type Goldfish with shorter-bodied Fancy Goldfish. ...."

I would get rid of the comet actually, I'm fairly sure this is the reason of bullying, and you never know, if the moor would die (which it easily might from the stress...), the comet might decide that it wants the tank for itself and bully the fantail as well.

As to why the other fish died, it's pretty easy to assume that they did because the biological filter was shocked from the combination of the new amount of fish and underfiltration. On a tank this size an external filter would be the *almost* only way to go as most internal filters can't handle 2000 liters per hour.

Anyway, I do hope you'll figure out a good way to solve this I'd look into a larger filter though, if I were you

The filter is an Aqua One 104F (2000L/hr), and I do a water change weekly using a plastic gravel cleaner thingy to just under the half way mark as well as clean the filter (and ornament and plants if they need it). I don't know much about the under gravel filter and air pump as that came with the tank.

I'm amazed the original fish survived at all as when we got the tank second hand it was so full of green slime that we (and the people that had it) were unsure how many fish were still in it. We came across the remains of at least one dead fish in amoungst the gravel. Obviously we went nuts cleaning everything so thoroughly but I'll never forget the stench (especially the 2hr drive home with the tank in the backseat of the 4x4)!

We have never had any problems with Bronzie being aggressive towards Goldie as far as we are aware they have always been together. I added the two new goldfish about a week after we got the tank, and the calico one died within a few days from memory. The cockabullies are only tiny (very similar to algae eaters) and they went in maybe a fortnight after the new goldfish but unfortunately didnt last long either. After loosing those too I havent added anything else.

For now the moor is in a large plastic fruit bowl - not ideal but its all I have. Perhaps if I reintroduce him along with a new fish or two that would help? I'll get some live plants too. As for suggesting to my partner that we "get rid of the comet" his exact words were "Like ****, get rid of the other two st*pid ones!" ...soo I guess thats not an option . I do have a large plastic outdoor pond in storage so he may end up in that eventually (when we find a new house with the room for it) and then I can stick to my beloved blackmoors!

You really shouldn't keep the poor thing in that bowl... always separate the aggressive one, not the victim. This is only unduly stress for the already panicked fish.If you have a plastic box or something, make a few holes, hang it on the inside of the tank by the edge and pop the comet in. However, I'd just bring it back to the pet shop since your tank most likely is full with the moor and fantail alone. How big is it? (For the size of your filters, it shouldn't be much bigger than an 80-100 liter..)

May I ask how big is the large plastic out door pond?Depending on it's size, you could move the comet in there and I am sure it would appreciate the extra swimming room!Does the pond have a filter with it already?

I have never heard of a black moor being aggressive, so he wouldn't have antagonized Goldie in anyway. It can sometimes happen that when a single tailed is kept with a fancy variety, that the aggression doesn't start until the single tailed has grown. Or if the fish have been kept in a small tank and are upgraded to the larger, with the extra swimming room the single tail can become aggressive that way.

I have heard of people using vegetable baskets as an isolation area for fish that are bullying, as they already have holes and I believe they float?